1. Field of the Invention
The present invention relates to an illuminator that allows a wide luminous intensity distribution.
2. Description of the Related Art
Conventionally, when considering light sources for a general lighting purpose used, for example, in indoor situations, an incandescent lamp or a fluorescent lamp has been used; however, through today's technical advancement of blue light-emitting diodes (the LEDs), the LEDs have come into use as the light sources applied to, for example, a ceiling light or a downlight. As one of the examples, FIG. 7 illustrates an edge-light type illuminator 7. This edge-light type illuminator 7 is composed of a light guide plate 1; LEDs 2A, 2A that are arranged at both opposed lateral end surfaces 2C, 2C of the light guide plate 1; a reflection sheet 3 that is arranged on the side of a reflective surface 1B opposed to an exit surface (a main surface 1A) of the light guide plate 1 where lights, which are emitted from the LEDs 2A, 2A and introduced into the opposed lateral end surfaces 2C, 2C of the light guide plate 1, exit out; and an approximately square-shaped diffusion sheet 6 that is arranged on the side of the main surface 1A of the light guide plate 1. A referential numeral 8 illustrates dot-shaped or strip-shaped optical elements that are arranged on the reflective surface 1B of the light guide plate 1, each of the optical elements being approximately formed into a circular, a dot, a square, and the like. In FIG. 7, a referential numeral 2B illustrates an LED array, a referential numeral 4 illustrates a reflector, and a referential numeral 5 illustrates a frame body 5. See, for example, Japanese Patent Application Laid-open No. 2010-225286.
FIG. 8A is now referred. Here, the light guide plate 1 and the diffusion sheet 6 exemplified in FIG. 7 are focused. To satisfy luminous intensity distribution properties of the illuminator provided with the light guide plate 1, a certain wide luminous intensity distribution is required. Here, however, only the provision of the diffusion sheet 6 may not be sufficient in many cases. In this case, as shown in FIG. 8B, the optical element 8 with a complicated contour may be arranged on the main surface 1A of the light guide plate 1. Accordingly, further wide luminous intensity distributions may be achieved. However, when needed to deal with large-sized illuminators, it becomes difficult to manage in case, for example, the contour of the illuminator is changed.